Currently, lighting accounts for a substantial percentage of electricity use in both the United States and world-wide. The lighting industry is moving away from low efficiency sources like tungsten filament lamps to Compact Fluorescent Lamps (CFL) and Solid State Lighting (SSL) based on Light Emitting Diodes (LED). While CFLs have better efficiency and efficacy than filament lamps, they suffer from high cost and environmental hazards. Also CFLs cannot easily be configured to produce beams of light because the etendue is large and the value of lumens per etendue unit is low.
LEDs, however, continue to improve in all performance and cost categories. The efficiency, efficacy and lumens per etendue unit for LEDs are all superior to both filament lamps and CFLs. SSL is desirable because of low power consumption, high efficacy, low heat load, lower operating temperature, smaller size, long life and reduced environmental concerns.
However, in beam forming applications the LED/SSL theoretical superiority in lumens per etendue unit has not been effectively utilized because of the difficulty of designing beam producing optics to accommodate the LED chip hemispherical Lambertian intensity distribution while producing the desired intensity profile in the target area (usually bell shaped or uniform). Direct substitution of LED emitters into optical designs originally intended for filament or arc lamps has been found wanting. This difficulty has been especially true for lighting fixtures (luminaires, and stage lighting instruments or lanterns) that generate beams of light. Spotlights, ellipsoidals, Fresnels, PAR cans and flood lights are examples of such beam generating luminaires. In contrast to such beam generating luminaires are room or area lighting, overhead fluorescent fixtures or the like.